This invention relates to rolling contact bearings, and more particularly to relubricatable, double-row bearings, especially those designed for use as roller turn rollers in conveyor applications.
Rolling contact bearings have long been used in a variety of applications. One type of rolling contact bearing is the double row bearing which includes an outer race member, two inner race members, and two rows of balls, or rollers, positioned between the outer race member and the inner race members.
To insure long life and smooth operation, such double-row bearings, and more particularly the balls or individual rollers in each row, must be lubricated so that the bearing will not dry out and fail due to lubrication starvation. Rolling contact bearing lubrication is facilitated primarily through two separate means. The first means is to position sealing means between the outer and inner race members at either end of the rolling contact bearing to retain lubricant in the bearing. The second means is to periodically relubricate the bearing through a passageway between the inner race members.
Usually, the two inner race members of a roller turn roller of the double-row variety described above are spaced one from the other to define a lubricant reservoir in conjunction with the outer race. This reservoir communicates with both rows of balls so that lubricant in the reservoir can travel to the rows to relubricate the balls. When the bearing is mounted for use using a hollow bolt passing through both inner race members, grease, or other suitable lubricant, can be introduced into the reservoir through the hollow bolt. Preferably, both a lubrication passageway and some type of seal are included in a roller turn roller to insure adequate lubrication.
When double-row rolling contact bearings are mounted along a generally vertical axis, lubrication difficulties become more acute. Any lubricant on the upper row tends to migrate downwardly due to the influence of gravity. Consequently, the upper row can fail much more quickly than the lower row due to lubricant starvation, while the lubricant in the reservoir tends to settle around and cause excessive lubrication of the lower row of balls.
Prior artisans have developed a variety of devices in an attempt to arrest excessive lubricant flow to the lower row while insuring adequate flow to the upper row. One such approach is to include a cylindrical spacing sleeve having at least one aperture therein between the inner race members, forming a reservoir defined by the sleeve, the outer race member, and the inner race members. Lubricant is introduced into the reservoir through a hollow bolt and the aperture in the sleeve to pressurize the reservoir. The grease in the reservoir under pressure tends to flow both upwardly and downwardly to lubricate both rows of balls. However, the pressurized grease also tends to settle around, and be lost past, the lower row of balls. Additionally, the reservoir is relatively large, requiring a large charge of lubricant during relubrication.
Prior artisans have also used washers on either side of the spacer sleeve adjacent both inner race members in double-row bearings. The washers have an outer diameter only slightly smaller than the inner diameter of the outer race member so that a restricted opening is defined between the grease reservoir and both rows of balls. Because of the restricted opening, the pressurized grease in the reservoir was arrested in its flow downwardly to the lower row of balls and out of the bearing. This approach also has its drawbacks. First, a relatively large grease reservoir exists in the bearing, requiring a large charge of grease to fill the bearing. Second, the construction requires several parts, further requiring relatively complex assembly.
Another approach taken is to replace the flat washers described above with dished washers. This approach also suffers the drawbacks of requiring several parts, complicated assembly, and a relatively large grease reservoir, requiring excessive amounts of grease to lubricate the bearing. Further, neither the flat nor dished washers totally prevent downward lubricant migration.
Although steps have been taken to reduce the volume of the lubricant reservoir, these have not been satisfactory. One bearing includes an outer race member having an inner wall extending into the reservoir to reduce the volume thereof. A second approach enlarged the cylindrical spacing sleeve to restrict the reservoir. However, these bearings are not typically relubricatable. Further, such bearings do not include means between the reservoir and the rows of balls for controlling the flow of grease therebetween.